Synthesis and characterization of fluorinated polyamide bearing pyridine and triphenylphosphine oxide moieties

An aromatic diamine with a pyridine unit and a trifluoromethyl pendant, 4-(4-trifluoromethylphenyl)-2, 6-bis(4-aminophenyl)pyridine, was successfully synthesized via modified Chichibabin reaction of 4-trifluoromethylbenzaldehyde and 4-nitroacetophenone, followed by catalytic hydrogenation using hydrazine hydrate and Pd/C catalyst in refluxing ethanol, which was employed to prepare fluorinated polyamide bearing pyridine and triphenylphosphine oxide moieties with bis(4-chloroformylphenyl) phenyl phosphine oxide through low temperature polycondensation. The resulted polyamide was characterized by FT-IR, DSC, TGA and WAXD, etc. The polyamide with inherent viscosity of 0.98 dL/g is amorphous and exhibits a high transparency with the ultraviolet-visible absorption cut-off wavelength of 329 nm. The glass transition temperature (Tg) is 291°C, decomposition temperature (Td) at 10% mass loss is 540°C and char yield is 64% at 800°C in N2. This polyamide can be readily soluble in organic solvents such as N, N-dimethylacetamide (DMAc), N, N-methyl-2-pyrrolidone, m-cresol, pyridine and tetrahydrofuran. Transparent, flexible, and tough film of the polymer cast from DMAc solution exhibits tensile strength of 86 MPa, elongation at break of 10%, tensile modulus of 2.0 GPa. This polyamide indicates excellent electrical resistance properties, such as the volume resistivity of 8.62×1015Ω·cm, surface resistivity of 9.85×1014 Ω and dielectric constant of 3.48 (100 Hz).